Computer systems typically include multiple peripheral devices coupled to the system via communication buses. Often these peripherals are coupled to buses through expansion cards (also known as adapter cards) that plug into expansion card connectors (or slots) on the motherboard. The communication buses are generally fault-intolerant, so that failure or aberrations at the expansion card or expansion card connector may adversely affect the ability of the communication bus to effectively transmit data. A common cause of such failure in a computer system is the insertion into or removal of an expansion card from a connector when that connector is powered and running. In an effort to prevent these types of problems, some standards and specification have been developed. For example, the PCI (Peripheral Communication Interface) “Hot Plug” specification governs insertion into and removal of expansion cards from communication buses while the computer system is running. Since expansion cards are generally not designed to be inserted in a powered connector, the specification defines a sequence of user actions and system behavior to ensure that power is removed from the connector before the expansion card is inserted. This specification requires slot specific power switches to control power to each slot, and often such power switches are physical switches that can be manually activated to turn power to the slot on or off. The specification further suggests the use of slot state indicators, such as LEDs, to indicate to a user whether the connector is powered on or off (the power state of the connector), and the error status of the slot. Many prior art systems utilize both a physical power switch and an LED slot state indicator for each connector.
In any system having such an LED indicator and power switch associated with a connector, it is important to make these devices readily accessible to a user. A system that requires removal of computer system covers or access panels to view the LED is undesirable, as is a system having a power switch that is difficult to access. Many prior art systems have addressed these concerns by placing the LED indicators and power switches for each card slot on a separate printed circuit board that is electrically coupled to the motherboard. This separate printed circuit board is mounted inside the back side of the computer housing in such a way that at least the LED indicator is visible from the outside of the computer housing through an aperture or the like in the computer housing. In this manner, a user can determine the status of a card slot without removing the computer housing. In some systems, the power switches are also accessible in this way.
Drawbacks of the above described prior art systems include the increased cost of having a separate printed circuit board containing LED indicators (or any other indicator that conveys the power status of the connector) and possibly power switches, in addition, the difficulty in electrically coupling this separate printed circuit board to each expansion connector. Systems having these additional components also inherently have more modes of failure.
Other prior art systems have used translucent devices to transfer light emitted from an LED on the printed circuit board to a point near the top of a protective divider that separates successive expansion card connectors and expansion cards. In these known devices, however, light is not visible from an exterior of the computer housing. Thus, the housing must be removed, or partially removed, to view the LED and to access the power switch.
It would be advantageous to provide a simplified system and method for indicating to a user the power status of an expansion card connector and for controlling power to that connector.